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Projection of pulmonary rapidly adapting receptors to the medulla of the cat: an antidromic mapping study.
Projection of pulmonary rapidly adapting receptors to the medulla of the cat: an antidromic mapping study.
- Source :
-
The Journal of physiology [J Physiol] 1986 Apr; Vol. 373, pp. 63-86. - Publication Year :
- 1986
-
Abstract
- The activity of pulmonary rapidly adapting receptor (r.a.r.) neurones was recorded extracellularly in the nodose ganglion of the decerebrate cat. The receptors were identified by their rapid adaptation to 'ramp and hold' hyperinflations of the lung. The antidromic mapping technique was used to determine the sites of projection and branching patterns within the nucleus of the tractus solitarius (n.t.s.) of eleven r.a.r.s. The medulla was explored with a stimulating electrode to activate the r.a.r.s. antidromically. In each penetration, depth-threshold measurements were made for each antidromic response characterized by a distinct latency. Using the anatomical sites of the minimum threshold points, the locations of central branches of individual r.a.r.s. were determined. The main axons of all of them coursed within the tractus solitarius (t.s.) at levels from 2 mm rostral to 0.5 mm caudal to the obex. The axonal conduction velocities within the t.s. were 6.2-9.7 m/s, where the peripheral conduction velocities were 11.2-20.4 m/s (28 degrees C). Different latencies of response evoked in a single penetration were considered to indicate branching. The densest branching was found in the ipsilateral commissural subnucleus of the n.t.s. at levels 0.3-1.3 mm caudal to the obex and, to a lesser degree, in the contralateral commissural subnucleus. All r.a.r.s. sent a few branches to the medial n.t.s. rostral to the obex. Four r.a.r.s. ramified in the ventrolateral n.t.s. where inspiratory cells are located. Depth-threshold graphs were interpolated by best fitting parabolic equations: Ith = Ad2 + Bd + C; where Ith is the threshold current, d the corresponding depth of stimulation, and A, B and C are coefficients. Coefficient A is a measure of steepness of the parabola. The A coefficients were inversely related to the conduction velocity (v) of the stimulated branch. An analysis of the data from the present study (v = 5.0-9.7 m/s) combined with data from the literature (v = 2.2-85 m/s) led to a simple relationship between the A coefficient and the conduction velocity of the stimulated fibre: A = 6500/v, where A is expressed in microA/mm2 and v is expressed in m/s. Within the range 3-35 m/s, the formula is useful in predicting the effective current spread when the conduction velocity is known, or to estimate the conduction velocity from the shape of a depth-threshold curve. Two slowly adapting pulmonary stretch receptors (p.s.r.s) were studied.(ABSTRACT TRUNCATED AT 400 WORDS)
- Subjects :
- Action Potentials
Afferent Pathways physiology
Animals
Axons physiology
Brain Mapping
Cats
Female
Male
Medulla Oblongata cytology
Neural Conduction
Nodose Ganglion cytology
Nodose Ganglion physiology
Sensory Thresholds physiology
Time Factors
Lung innervation
Medulla Oblongata physiology
Neurons, Afferent physiology
Sensory Receptor Cells physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0022-3751
- Volume :
- 373
- Database :
- MEDLINE
- Journal :
- The Journal of physiology
- Publication Type :
- Academic Journal
- Accession number :
- 3746682
- Full Text :
- https://doi.org/10.1113/jphysiol.1986.sp016035